Account Energy Dissipation Research Articles

Superconducting qubit in a nonstationary transmission line cavity: Parametric excitation, periodic pumping, and energy dissipation

We consider a superconducting qubit coupled to the nonstationary transmission line cavity with modulated frequency taking into account energy dissipation. Previously, it was demonstrated that in the case of a single nonadiabatical modulation of a cavity frequency there are two channels of a two-level system excitation which are due to the absorption of Casimir photons and due to the counterrotating wave processes responsible for the dynamical Lamb effect. We show that the parametric periodical modulation of the resonator frequency can increase dramatically the excitation probability. Remarkably, counterrotating wave processes under such a modulation start to play an important role even in the resonant regime. Our predictions can be used to control qubit-resonator quantum states as well as to study experimentally different channels of a parametric qubit excitation.

On the energy dissipation rate at the inner edge of circumbinary discs

We study, by means of numerical simulations and analysis, the details of the accretion process from a disc onto a binary system. We show that energy is dissipated at the edge of a circumbinary disc and this is associated with the tidal torque that maintains the cavity: angular momentum is transferred from the binary to the disc through the action of compressional shocks and viscous friction. These shocks can be viewed as being produced by fluid elements which drift into the cavity and, before being accreted, are accelerated onto trajectories that send them back to impact the disc. The rate of energy dissipation is approximately equal to the product of potential energy per unit mass at the disc's inner edge and the accretion rate, estimated from the disc parameters just beyond the cavity edge, that would occur without the binary. For very thin discs, the actual accretion rate onto the binary may be significantly less. We calculate the energy emitted by a circumbinary disc taking into account energy dissipation at the inner edge and also irradiation arising there from reprocessing of light from the stars. We find that, for tight PMS binaries, the SED is dominated by emission from the inner edge at wavelengths between 1-4 and 10 $\mu$m. This may apply to systems like CoRoT 223992193 and V1481 Ori.

Energy-network performance trade-off in a slotted IEEE 802.15.4 network with acknowledged uplink transmissions

This paper provides an analysis of the performance of wireless sensor network WSN under the beacon-enabled slotted CSMA/CA of IEEE 802.15.4 Standard in non-saturation mode with acknowledged uplink and limited buffers. The performance metrics of a node considered are: reliability, average throughput per node, average packet delay and average energy consumption. An analytical model of energy is derived and used to analyse the average consumption of node. This model takes into account energy dissipation of the radio unit and also of the processing and the sensor units. All these performance metrics are evaluated with different parameters such as medium access control MAC parameters, network density and offer load per node in order to observe their influence and adjust them if necessary to obtain good performance.

Mathematical modeling and calculation of forced resonant vibrations of composite electromechanical system

Resonant vibrations of composite electromechanical symmetric three-element system “metal plate - piezoceramic cylindrical panels” are considered. Forced vibrations are made under the influence of external alternating electric field, supplied to the electrodes of piezoceramic segments of cylindrical panels, previously polarized in the tangential direction. Based on the improved theory, such as the S.P. Timoshenko’s, the system of differential equations of forced vibrations of the system, taking into account energy dissipation of relatively radial and tangential displacements, turning angle of the normal to the panel surface and longitudinal displacements of the plate is written. For the closure of the equation system, boundary conditions - kinematic and dynamic conditions of connecting cylindrical piezoceramic panels with the metal plate are formulated and written. Integration of the full system of differential equations of vibration is performed, the dependence of radial displacements of panels and longitudinal displacements of plates on the vibration frequencies in the range, which includes the first two working resonant frequencies are found. Amplitude-frequency characteristics of vibrations on the example of the central point of the panel (maximum radial displacements) and the end point of the plate (maximum longitudinal displacements) are built. Evaluation of the stress-strain state of the studied electromechanical system on the frequency of principal resonance considering energy dissipation is carried out.

Cascades of Velocity and Temperature Fluctuations in Buoyancy-Driven Thermal Turbulence

Direct multipoint measurements of the velocity and temperature fields have been made in a turbulent Rayleigh-Bénard convection cell. In the central region of the cell it is found that both velocity and temperature exhibit the same scaling behavior that one would find for the velocity and for a passive scalar in homogeneous and isotropic Navier-Stokes turbulence. This is despite the fact that energy is pumped into the system vertically via buoyancy. Near the cell's sidewall where thermal plumes abound, vertical velocity and temperature exhibit different scalings. A model that takes into account both buoyancy and energy dissipation is proposed and its predictions agree well with the sidewall experimental results.

A bubble fission model for collapsing cavitation bubbles

A bubble fission model that takes into account energy dissipation during violent collapses of cavitation bubbles is introduced by assuming volume conservation and continuity of the gas pressure during instantaneous breakup, invoking either Rayleigh–Taylor instability or high speed microjet formation. In particular, a modified Rayleigh–Plesset equation is derived for the volumetric motion of the fission fragments in rebound. Results obtained under a pressure signal typical for cavitation bubbles confirm the scaling law of Brennen [C. E. Brennen, “Fission of collapsing cavitation bubbles,” J. Fluid Mech. 472, 153 (2002)] and the observations in experiments.

Explosive Compaction: the Type of Microstructure of Contact Boundaries Produced by Formation of a Strong Bond

This paper studies the microstructure of the contact zones during formation of a strong joint and its dependence on the loading parameters and the characteristics of the compacted fraction. It is shown that a strong bond forms when highly fragmented microstructure is produced in the contact zone as a result of intense plastic deformation. The formation of such microstructure on the maximum surface area of pressed particles is made possible by optimizing the compaction procedure and the powder particle size and by taking into account energy dissipation in the contact zone.

Causal viscosity in accretion disc boundary layers

The structure of the boundary layer region between the disc and a comparatively slowly rotating star is studied using a causal prescription for viscosity. The vertically integrated viscous stress relaxes towards its equilibrium value on a relaxation timescale τ, which naturally yields a finite speed of propagation for viscous information. For a standard α prescription with α in the range 0.1 – 0.01, and ratio of viscous speed to sound speed in the range 0.02 – 0.5, details in the boundary layer are strongly affected by the causality constraint. We study both steady state polytropic models and time dependent models, taking into account energy dissipation and transport. Steady state solutions are always subviscous with a variety of Ω profiles which may exhibit near discontinuities. For α=0.01 and small viscous speeds, the boundary layer adjusted to a near steady state. A long wavelength oscillation generated by viscous overstability could be seen at times near the outer boundary. Being confined there, the boundary layer remained almost stationary. However, for α=0.1 and large viscous speeds, short wavelength disturbances were seen throughout which could significantly affect the power output in the boundary layer. This could be potentially important in producing time dependent behaviour in accreting systems such as CVs and protostars.

Disk-Corona Models and X-Ray Emission from Seyfert Galaxies

AbstractThe current status of understanding of the X-ray emission from Seyfert galaxies involves Comptonization of soft photons by hot subrelativistic electrons. After briefly reviewing the early theoretical basis for the presence of hot optically thin plasma in or around accretion disks and the key observations that led to develop the presently popular model of an accretion disk with a hot corona, we summarize recent progress in accretion models that take into account energy dissipation and/or angular momentum transport in the corona. Finally, adopting the simple scheme of a homogeneous plane parallel corona, we discuss in detail the dependence of the X-ray spectrum on the coronal parameters. Despite the strong coupling between optical depth and temperature which determines a spectral shape insensitive to their precise values, moderate spectral changes are possible. The spectral variability patterns can be used as diagnostics for coronal physics and should allow to determine whether the optical depth of the corona is dominated bye+e−pairs.

Modeling of the Ion-Beam Growth of Covalently-Bonded Diamondlike Materials

ABSTRACTA characteristic ion energy and substrate temperature dependence for the formation of tetra-hedral amorphous carbon (ta-C), cubic boron nitride (c-BN) and related diamondlike materials by ion deposition has been experimentally observed. We present an analytical model for diamondlike film growth that describes the transient modification of the film structure by successive individual ion impact events. Each ion impact is treated as a cylindrical thermal spike with a finite initial width, taking into account energy loss and energy dissipation processes. We show that rearrangement of atoms during a cylindrical spike is the dominant mechanism leading to the formation of the diamondlike phase. The model explains quantitatively the observed ion energy dependence of the sp3 bond fraction in ta-C, as well as the broad range of ion energies for which c-BN growth is observed.

Mathematical model for multisectional shakeout assemblies taking into account energy dissipation

We propose a mathematical model for the performance of a multisectional shakeout assembly whose seriesparallel inertial elements are connected by elastic linkages. The system executes plane-parallel motion. The interaction of the process load with the working members is modeled by unidirectional elastic linkages in the presence of dry static friction forces. Energy dissipation occurs in the contact zone between the process load and each grate, and also in the elastic linkages. In order to solve the system of nonlinear equations, we developed the application program package STEND-2 in the FORTRAN-IV programming language. The model allows us to determine efficient parameters for multisectional assemblies in the planning stage.

Interactive Base‐Isolation Foundation System: I. Finite Element Formulation

A finite element model to study the effects of seismic base isolation on the response of structures supported on pile foundations is presented. The model takes into account both pile flexibility and energy dissipation and radiation, realized through the mechanism of soil‐pile‐structure interaction. The resulting dynamic characteristics are considerably different from those of the structure with a fixed base. The model is applied to study the influence of soil‐pile‐structure interaction on the response of structures, including nonlinear pile‐soil effects. To incorporate nonlinearities in the soil‐pile system that might arise from large deformations under severe earthquake loading, the piles are modeled as beam‐column finite elements with material and geometric nonlinearities, while the soil is idealized by nonlinear springs and dashpots uniformly attached to the piles along their length. For the soil springs, a modified Ramberg‐Osgood model is employed. For the material damping of the soil, a simple relati...

Some problems of nonisothermal steady flow of a viscous fluid

The paper presents solutions to the problems of plane Couette flow, axial flow in an annulus between two infinite cylinders, and flow between two rotating cylinders. Taking into account energy dissipation and the temperature dependence of viscosity, as given by Reynolds's relation μ=μ0 exp (−βT) (μ0, β=const). Two types of boundary conditions are considered: a) the two surfaces are held at constant (but in general not equal) temperatures; b) one surface is held at a constant temperature, the other surface is insulated. Nonisothermal steady flow in simple conduits with dissipation of energy and temperature-dependent viscosity has been studied by several authors [1–11]. In most of these papers [1–6] viscosity was assumed to be a hyperbolic function of temperature, viz. μ=μm 1/1+α2(T−Tm. Under this assumption the energy equation is linear in temperature and can he easily integrated. Couette flow with an exponential viscosity-temperature relation. μ=μ0 e −βT (μ0, β=const), (0.1) was studied in [7, 8]. Couette flow with a general μ(T) relation was studied in (9). Forced flow in a plane conduit and in a circular tube with a general μ(T) relation was studied in [10]. In particular, it has been shown in [10] that in the case of sufficiently strong dependence of viscosity on temperature there can exist a critical value of the pressure gradient, such that a steady flow is possible only for pressure gradients below this critical value. In a previous work [11] the authors studied Polseuille flow in a circular tube with an exponential μ(T) relation. This thermohydrodynamic problem was reduced to the problem of a thermal explosion in a cylindrical domain, which led to the existence of a critical regime. The critical conditions for the hydrodynamic thermal “explosion” and the temperature and velocity profiles were calculated. In this paper we treat the problems of Couette flow, pressureless axial flow in an annulus, and flow between two rotating cylinders taking into account dissipation and the variation of viscosity with temperature according to Reynolds's law (0.1). The treatment of the Couette flow problem differs from that given in [8] in that the constants of integration are found by elementary methods, whereas in [8] this step involved considerable difficulties. The solution to the two other problems is then based on the Couette problem.